Previously, manganese complexes have been proposed as catalysts to enhance the activity of peroxygen bleaches such as hydrogen peroxide, hydrogen peroxide liberating or generating compounds and inorganic and organic peroxyacids. Such complexes include manganese-gluconate complexes, as described in EP-A-237 111, and manganese polyol complexes, as described in EP-A-443 651.
The effective amount of such complexes required in detergent and/or bleach compositions is very small, of the order of hundredths of a percent. Problems associated with the use of such small quantities include achieving an accurate dosage and homogeneous distribution of the complex throughout the composition. Inhomogeneity in the distribution of the complex may result in an inconsistent performance of the detergent and/or bleach composition.
Good distribution of the complex in a composition may be achieved by spraying a solution thereof, onto a base detergent formulation. However, this has its disadvantages in that direct contact between the manganese complex and other components present, for example nonionic detergent active and peroxygen bleaching agent, may result in a reduction in the level of these active components as a result of adverse redox reactions.
Another option would be to mix pure crystals of the manganese complex with the base detergent and/or bleach formulation. However, this may also result in interactions between individual components with consequential losses in levels of active materials.
In particular, interaction between the manganese complex and a peroxide bleach may result in rapid decomposition of the bleach during storage.
A further problem which may arise when manganese is incorporated in a base formulation is the formation of brown inactive manganese dioxide during storage and/or upon powder dissolution.
Previously, in order to overcome such problems, it has been proposed to form heavy metal complexes into agglomerates prior to addition to a detergent base formulation. An example is U.S. Pat. No. 4,626,373 which teaches manganese complexes, comprising Mn(II) and a ligand such as ethylenediamine tetraacetic acid or diethylene triamine pentaacetic acid, may be protected by encapsulating them in a matrix of a water-soluble or water-dispersible material.
The present invention is particularly concerned with a highly reactive manganese complex catalyst, as described in EP-A-0 458 397 and EP-A-0 458 398, and derivatives thereof.
EP-A-0 544 440 is concerned with such manganese complex catalysts and suggests overcoming the aforementioned problems by forming non-friable composite granules comprising the complex, a binding agent such as a polymer, a silicate or fatty acid/soap mixture and, optionally, an inert salt such as a chloride or carbonate.
Another suggestion, taught by our copending International Patent Application PCT/EP94/00640 (corresponding to UK Patent Application 9305598.6) involves forming granules comprising the complex; a carrier material selected from zeolite, alkali metal sulphate, citric acid, succinic acid and starch; and a binding agent selected from water-soluble non-oxidisable polymers, alkalimetal silicates and saturated fatty acid soap.